Method for constructing a floating roof tank

ABSTRACT

A method for constructing a floating roof tank without using a high scaffold within the tank, wherein, when a side wall of the tank is built up to a certain level, a number of short angle supports are errected on a bottom plate of the tank for forming a floating roof thereon by assembling and welding a deck plate and a number of pontoons. After sealing a gap between the side wall of the tank and the pontoons, air is blown into a closed space beneath the assembled floating roof to lift the same up horizontally to a predetermined level with the aid of a pulling means. The floating roof is maintained at the lifted level to make a working space thereunder for carrying out the necessary works.

United States Patent [191 Hirota Sept. 2, 1975 [54] METHOD FORCONSTRUCTING A 3,106,772 10/1963 Holcombe 29/429 FLOATING ROOF TANK3,315,343 4/1967 Berg 29/421 [75] Inventor: Takao Hirota, Tokyo, JapanPrimary Examiner c w Lanham [73] Assignee: T0y0 Kan t ll y JapanAssistant Examiner-Victor A. DiPalma [22] Filed: Nov. 8, 1974 21 Appl.No.: 522,016 [57] ABSTRACT A method for constructing a floating rooftank without [30] Foreign Application Priority Data using a highscaffold within the tank, wherein, when a N 15 1973 J 48 128632 sidewall of the tank is built up to a certain level, a apan number of shortangle supports are errected on a bottom plate of the tank for forming afloating roof [52] US. Cl 29/454, 29/421 thereon by assembling andWelding a deck plate and a 5] I t Cl B23 19/04 number of pontoons. Aftersealing a gap between the d 436 side wall of the tank and the pontoons,air is blown 1 1e 0 earc i into a closed space beneath the assembledfloating roof to lift the same up horizontally to a predetermined levelwith the aid of a pulling means. The float- [56] References Clted ingroof is maintained at the lifted level to make a UNITED STATES PATENTSworking space thereunder for carrying out the neces- 2,304,354 12/1942Harvey 1 13/120 R sary w0rks 2,511,873 6/1950 Perkins 113/120 R X3,057,054 10/1962 Barnes 29/429 8 Claims, 2 Drawing Figures METHOD FORCONSTRUCTING A FLOATING ROOF TANK BACKGROUND OF THE INVENTION Thisinvention relates to a method for constructing a floating roof tank.More particularly, the invention concerns a method for constructing afloating roof tank, which can contribute to facilitate the constructionwork and at the same time to reduce the amount or number of scaffoldingmaterials and working equipments to a considerable degree as comparedwith the conventional methods.

In the construction of floating roof tank, it has thus far been theusual practice to build a high scaffold like a spider web within thetank to form a floating roof thereon by assembling a number of pontoonsand a deck. The assembling work on a high scaffold is dangerous andusually involves serious accidents of the workmen. In addition, the roofconstruction employing a high scaffold takes a lot of time in assemblingand disassembling the scaffold as well as in transferring a large amountof materials to and from the construction site which is usually remotefrom a storage place, obviously resulting in a prohibitively highconstruction cost.

SUMMARY OF THE INVENTION:

It is therefore an object of the instant invention to provide a methodfor constructing a floating roof tank, which will eliminate thedrawbacks inherent to the conventional methods as mentioned above.

It is a more particular object of the present invention to provide amethod for constructing a floating roof tank, which does not necessitateerrection of a high scaffold within the tank.

It is a further object of the present invention to provide a method forconstructing a floating roof tank, which involves only a reduced numberof steps.

It is still another object of the present invention to provide a methodfor constructing a floating roof tank, which can significantlyfacilitate the construction work while reducing the construction cost toa material degree.

An one preferred form of the invention, the method comprises the stepsof erecting a number of short angle supports on a bottom plate of a tankwhen a side wall of said tank is built up to a given level; forming afloating roof and on the errected angle supports by securely welding adeck and a number of pontoons to each other; securing inflatable sealingmeans around the outer periphery of the connected pontoons; feedingcompressed air to said sealing means for hermetically sealing a gapbetween said side wall of said tank and said pontoons; blowing air intoa closed space beneath said floating roof to float the same horizontallyup to a predetermined level with aid of pulling means to make a workingspace beneath said roof; and fixing said roof at the elevated level on anumber of support columns of a predetermined length.

The above and other objects, features and advantages of the presentinvention will become clear from the following particular descriptionand the appended claims, taken in conjunction with the accompanyingdrawing which shows by way of example a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS:

In the accompanying drawing:

FIG. 1 is a diagrammatic sectional view generally showing a floatingroof tank under construction according to the method of the invention;and

FIG. 2 is a fragmentary sectional view showing on an enlarged scale oneportion of the tank of FIG. 1.

PARTICULAR DESCRIPTION OF THE INVENTION:

The present invention is now described more particularly with referenceto the accompanying drawing. Referring to FIGS. 1 and 2, when the sidewall of a tank 1 is built up to a suitable level as shown at 2, forexample, to the level of the second row, a number of low workingsupports 4 is erected on a bottom plate 3 of the tank with use of shortangle or round steels having a length of, for example, 500 mm.Thereafter, a floating roof 7 is formed by assembling a deck plate 6 anda number of pontoons 5 with use of a crane or other suitable liftingmeans. The deck plate 6 and pontoons are welded hermetically to eachother, and a sealing means 8 having a rubber scarf band is fixed aroundthe outer periphery of the welded pontoons 5. The air sealing means 8 isconnected by means of an air feed pipe 14 to an air compressor 9 whichis located outside the tank 1. A blower 9 is fixedly mounted on the deck6 and has at its output end opened into the deck 6. A number ofapertured connecting pieces 13 are fixed securely on the pontoons 5 at asuitable distance from adjacent ones. At the same time, a correspondingnumber of similar apertured connecting pieces 13 are securely fixed onthe inner surface of the side wall 2 in vertical alignment or to formpairs with the apertured pieces 13 on the pontoons 5. A wire rope orchain 10 is threaded through the apertures 12, 12' of the upper andlower connecting pieces I3, 13. The wire rope 10 is fixed by a shacklel5 and is provided with a universal puller (hoisting chain block) 11 towind up the ropes or chains 10 as will be explained hereinlater.

After assembling the floating roof 7, compressed air is introduced intothe sealing means 8 from the air compressor 9' to hermetically seal thegap between the side wall (shell plate) 2 and the pontoons 5.Thereafter, air is blown into the hollow closed space below the floatingroof7 from the blower 9 on the deck 6 to float the roof 7. In thisinstance, in order to prevent inclinations or localized deformation ofthe roof 7, the wire rope or chain 10 is wound up by means of the puller11 to lift the floating roof 7 in a horizontal state up to a suitablelevel to make a working space beneath the roof 7, for example, up to aheight of 1900 mm on a scale 20 which is graduated on the inner surfaceof the side wall 2. As soon as the floating roof 7 reaches thepredetermined level, a number of openings are bored through the pontoonsand the deck plate for inserting therethrough support guide pipes orsleeves 17 each with a pin hole 19. The support guide pipes 17 are fixedin the respective openings, each slidably receiving therethrough asupport column 18 with a pin hole 19. The support guide pipes 17 arefixed on the support columns by inserting and fixing pins in the pinholes 19 and 16 of the support columns 18 and the support guide pipes17. After fixing the support guide pipes 17, the amount of air from theblower 9 is gradually reduced. The blower 9 is switched off afterconfirming that the lower ends of the respective support columns arelowered to the level of the bottom plate 3. In this manner, a workingspace is made under the roof 7 to carry out the necessary work.

It will be understood from the foregoing description that, according tothe method of the present invention, the construction of the floatingroof tank may be completed without using a high scaffold so that itbecomes possible to reduce the costs which would otherwise be incurredin connection with procuration, transportation and errection ordisassembling of the scaffold materials. For example, for theconstruction of a 160,000 KI tank, it has thus far been required toerrect a scaffold having a height of about 1800 mm, using about 110 tonsof scaffold materials including channel and angle steels. The removal ofsuch a scaffold after completion of the work usually takes at leastthree days by eight workmen. However, the method according to theinvention does not necessiate the errection of a high scaffold, and thedeck support can be formed with use of only 9 tons of 500 mm long anglesteels and removed in only two hours by two workmen.

in addition, according to the present invention, the construction workcan be carried out on low deck supports in a far safer manner ascompared with the conventional methods. As mentioned hereinbefore. thecost and time of the construction can be reduced to a considerabledegree since the necessary construction work can be carried out with useof a reduced amount of materials and few equipments. including acompressor, blower and pulling wire ropes or chains. Moreover, levelingof the floating roof is carried out by means of the hoisting blocks sothat any types of floating roof tank, such as a center pontoon typctank, a buoy roof type tank. a tank having double deck roof and so on.can be constructed by the present invention.

What is claimed is:

l. A method for constructing a floating roof tank, comprising the stepsof:

erecting a number of short angle supports on a bottom plate of said tankafter building a side wall up to a given level;

forming a floating roof on said angle supports by connecting pontoonsaround a deck plate;

securing inflatable sealing means around the outer periphery of saidpontoons;

feeding compressed air to said sealing means for hermetically sealing agap between said side wall and said pontoons;

blowing air into a closed space beneath said floating roof to float thesame horizontally up to a predetermined level with the aid ofa pullingmeans to make a suitable working space beneath said roof; and

fixing said roof at the elevated level by means of a number of supportcolumns.

2. A method according to claim 1, wherein compressed air is fed to saidsealing means from an air compressor which is located outside said tank.

3. A method according to claim 1, wherein air is blown into said closedspace by a blower which is mounted on said floating roof.

4. A method according to claim 1, wherein said floating roof is pulledby winding up pulling means which are spanned between said side wall andsaid pontoons.

5. A method according to claim 4, wherein said pulling means are anumber of wire ropes.

6. A method according to claim 4, wherein said pulling means are anumber of chains.

7. A method according to claim 4, wherein each of said pulling means hasa universal puller at a suitable position within the length thereof.

8. A method according to claim 1, wherein said inflatable sealing meansis a scarf band securely connected to the outer periphery of saidpontoons.

1. A method for constructing a floating roof tank, comprising the stepsof: erecting a number of short angle supports on a bottom plate of saidtank after building a side wall up to a given level; forming a floatingroof on said angle supports by connecting pontoons around a deck plate;securing inflatable sealing means around the outer periphery of saidpontoons; feeding compressed air to said sealing means for hermeticallysealing a gap between said side wall and said pontoons; blowing air intoa closed space beneath said floating roof to float the same horizontallyup to a predetermined level with the aid of a pulling means to make asuitable working space beneath said roof; and fixing said roof at theelevated level by means of a number of support columns.
 2. A methodaccording to claim 1, wherein compressed air is fed to said sealingmeans from an air compressor which is located outside said tank.
 3. Amethod according to claim 1, wherein air is blown into said closed spaceby a blower which is mounted on said foating roof.
 4. A method accordingto claim 1, wherein said floating roof is pulled by winding up pullingmeans which are spanned between said side wall and said pontoons.
 5. Amethod according to claim 4, wherein said pulling means are a number ofwire ropes.
 6. A method according to claim 4, wherein said pulling meansare a number of chains.
 7. A method according to claim 4, wherein eachof said pulling means has a universal puller at a suitable positionwithin the length thereof.
 8. A method according to claim 1, whereinsaid inflatable sealing means is a scarf band securely connected to theouter periphery of said pontoons.